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  • 1,2-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline  (1)
  • 6,7-dihydroxytetra-hydroisoquinolines  (1)
  • Keywords: 1(N)-Amino-4-phenyl-1  (1)
  • L-DOPA  (1)
  • 1
    ISSN: 1435-1463
    Keywords: Keywords: 1(N)-Amino-4-phenyl-1 ; 2 ; 3 ; 6-tetrahydropyridine ; oxidation ; monoamine oxidase ; MPTP ; MPP+ ; human brain synaptosomes.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. A 1-amino analog of MPTP, 1(N)-amino-4-phenyl-1,2,3,6-tetrahydropyridine, was synthesized and the oxidation was examined using human synaptosomal mitochondria as sources of type A and B monoamine oxidase. An oxidation product, 1-amino-4-phenylpyridinium ion, was quantified by high-performance liquid chromatography-fluorometric detection. The amino analog was a substrate of both type A and B monoamine oxidase and the oxidation depended linearly on the enzyme amount and the reaction time with an optimal pH around 7.5. After the systemic injection of the amino analog in C57/black mice for one week, 1-amino-4-phenylpyridinium ion was detected in the brain. 1(N)-Amino-4-phenyl-1,2,3,6-tetrahydropyridine was proved to be cytotoxic to pheochromocytoma PC12 cells, and it may be a new neurotoxin bioactivated through the oxidation by type A and B monoamine oxidase.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1463
    Keywords: Uptake ; inhibition ; dopamine transporter ; 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline ; 1,2-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline ; 1,2-dimethyl-6,7-dihydroxyisoquinolinium ion ; neuroblastoma SH-SY5Y cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Uptake of catechol isoquinolines to dopamine cells was studied using human dopaminergic neuroblastoma SH-SY5Y cells. Only (R)-1,2-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline [(R)-1,2-DiMeDHTIQ] was transported by dopamine uptake system, while (S)-1,2-DiMeDHTIQ, (R)- and (S)-1-methyl-6,7-dihydroxy-tetrahydroisoquinoline, and 1,2-dimethyl-6,7-dihydroxyisoquinolinum ion were not. Kinetical study showed that the uptake of (R)-1,2-DiMeDHTIQ followed the Michaelis-Menten equation, and the values of the Michaelis constant and the maximal velocity were obtained to be 102.6 ± 36.9 μM and 66.0 ± 2.8 pmol/min/mg protein. Dopamine was found to inhibit (R-1-DiMeDHTIQ uptake competitively. These results suggest that the selective uptake by dopamine transporter may account for the specific neurotoxicity of (R)-1,2-DiMeDHTIQ to dopamine neurons.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1435-1463
    Keywords: Tyrosine hydroxylase ; tryptophan hydroxylase ; monoamine metabolism ; L-DOPA ; L-5-hydroxytryptophan ; microdialysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Using a microdialysis technique, the rat striatum was perfused with NSD-1015, an inhibitor of aromatic L-amino acid decarboxylase, and the amount of L-3,4-dihydroxyphenylalanine (L-DOPA) and 5-hydroxytrytophan (5-HTP) accumulating in dialysate was measured as an index of in vivo activities of tyrosine hydroxylase and tryptophan hydroxylase. NSD-1015 increased the concentration of L-DOPA much higher than that of 5-HTP in a dose-related manner (1–100 μmol/L). In order to examine the relationship between dopaminergic and serotonergic neurons in the striatum, either 5-HTP or L-DOPA was injected intraperitoneally to rats pretreated with benserazide, an inhibitor of peripheral decarboxylase. 5-HTP administration increased 5-HTP, but decreased L-DOPA in a dose-dependent manner. Conversely, 5-HTP concentration decreased in an association with the increased content of L-DOPA following L-DOPA administration. The decrease of 5-HTP caused by L-DOPA administration was not as remarkable as that of L-DOPA by 5-HTP injection. These results suggest that L-DOPA and 5-HTP, the precursor amino acids for catecholamines and indoleamines, could affect mutually each other neuronal activity through the inhibition of their rate-limiting enzymes.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1435-1463
    Keywords: Type A and B monoamine oxidase ; inhibitors ; 6,7-dihydroxytetra-hydroisoquinolines ; salsolinols ; human brain synaptosomal mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 6,7-Dihydroxy-1,2,3,4-tetrahydroisoquinoline (norsalsolinol) and 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol), and their N-methylated derivatives were found to inhibit type A and B monoamine oxidase isolated from human brain synaptosomal mitochondria. N-Methyl-norsalsolinol, (R) and (S) enantiomer of salsolinol, and N-methyl-salsolinols inhibited type A monoamine oxidase competitively to the substrate, kynuramine, andR enantiomers were more potent inhibitors thanS enantiomers. The inhibition was reversible. Norsalsolinol induced positive cooperativity toward kynuramine. Both norsalsolinol and N-methyl-norsalsolinol inhibited type B oxidase non-competitively to the substrate, and their K1 values were much higher than those to type A. Types of inhibition of type A monoamine oxidase depended on the enzyme sources. Inhibition of monoamine oxidase by 6,7-dihydroxy-1,2,3,4-tetrahydroisoquinolines is discussed in relation to their chemical structures.
    Type of Medium: Electronic Resource
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